Coupler Truck Shorting

[Tootle]

First, my apologies to cwburfle, Bob and Wayne for not getting back before now…just too busy with things that aren’t as important as trains.

OK, so after having been so deftly “hijacked” I’ve decided to take back control of my thread.  Although, I must say I found Bob and Wayne’s exchanges both entertaining and enlightening.

Cwburfle: The baseplate is tightly mounted and on the correct axles.  The spring “is what it is” as they say.  Each similar spring and pickup roller combination I’ve looked at has the same characteristics; all the springs are relatively “soft” and the roller/bracket mechanism has a lot of play/slop in it.  My first inclination is to pursue a mechanical solution is this area, although I do like Bob’s solution as well.  Thanks very much for your help.

Lionelsoni: Bob, as always a solution that’s both elegant and to the point.  I may very well use this if I can’t figure out something to make those pickup rollers behave better.  Thanks for your help, and thanks also for helping Wayne with his circuit design work.  :)

Webenda: Wayne, thanks for asking the question about how Bob’s circuit operates…I was confused as well.  Thanks also for the work on the schematics…now I can actually build this if I need to.  If we can get Bob and you together we might have the start of a next generation “how to” and repair manual complete with schematics.  Hmmm…something to think about…?

Thanks again to all for your input and assistance.

Frank Silvia, 79-14309

[webenda]

What was I thinking? The RC input filter would not have worked the way I drew it. Corrected and edited image in my post. Great big thank you for pointing that out Bob.

[lionelsoni]

I'm afraid the 1-kohm resistor goes between the capacitor and the base, not between the diode and the capacitor.

[webenda]

Thank you Bob. I use MS Paint for schematics.

I incorporated the four changes I counted in your ECR and reposted the schematics above.

[lionelsoni]

Your schematic puts my ASCII-art to shame, Wayne.

I would make two changes to your AC version:

o  I would put the variable resistor in series with the charging resistor, which is the thing that one might want to adjust, to vary the voltage-time product that determines the delay in arming the circuit.  You pretty much want the transistor to turn on whenever there is field voltage.  Note that it is the transistor's being on most of the time when the locomotive is running that keeps the capacitor from charging--except during extended neutral periods.

o  I would use about 10-kilohms rather than1 kilohm in parallel with the capacitor that the field voltage charges (to handle any transistor leakage current), and put a 1-kilohm resistor in series with the transistor base and bump the capacitor up to about 33 microfarads, so that the base current lasts through the 17-millisecond period of the field-voltage waveform.

The two specific problems that he mentioned were, as I understood, opening of the tender coupler and an unintended momentary operation of the accessory.  My suggestion would take care of the former for sure; and he seemed to suggest that the latter was harmless; so he wouldn't need to remove the operating section.  Of course, there may be other unintended consequences; and he might well not want to go to the trouble of building my circuit.  (But it might interest others reading this topic.)

[webenda]

Tootle,

I hope CWBurfle has not given you a bad feeling about our trying to help you with your problem. We really are trying to help.

.

CWBurfle,

There have been 7 logical suggestions for trouble shooting or repair of, "The problem seems to be mainly with OTC lockons whereby the pickup roller shorts the center rail to the lockon blade while the pickup shoe is still in contact with the blade, thus energizing the coil and opening the coupler. "

1) ...shortening the OTC blades--Tootle
2) ...fitting smaller rollers--Tootle
3) ...relocate the OTCs and accessories to sidings--Tootle
4) What I have done with all my locomotives, postwar and modern, that have electromagnetic couplers is to install a circuit that I devised to allow them to uncouple anywhere. So I don't have a single blade-type uncoupling section on my layout.--Lionelsoni
5) I wonder whether a missing or weak spring lets the bracket move from side to side.--CWBurfle
6) Also, is the baseplate tight on the axles?--CWBurfle
7) Is the baseplate mounted to the correct axles?--CWBurfle

And some discussion...
I asked about the technique for operating electrocouples without an OTC or uncoupling section with blade rails and tried to show a schematic for how Lionelsoni successfully replaced his troublesome OTC or "blade" rail track sections.

Your commment, "So far, nobody else seems to have any ideas." was rude and egotistic.
Your comment, "How is Tootle supposed to get help when his thread has been hijacked?" is just plain ignorant.

I love you anyway, even with your faults, CWBurfle.

[cwburfle]

If Tootle eliminates the OTC, how will he operate the horse car and corral? I think the horse car has a pick-up shoe for the vibro-motor inside the car.

 

Nice try to tie in the original subject.
How is Tootle supposed to get help when his thread has been hijacked?

[webenda]

Thank you Bob, that helps a lot.

Back to the drawing board

DC Operation

AC Operation

If Tootle eliminates the OTC, how will he operate the horse car and corral? I think the horse car has a pick-up shoe for the vibro-motor inside the car.

[lionelsoni]

Not exactly.  I did try operating the coupler directly from the capacitor at first; but the low coil resistance meant that the pulse was very short with any practical capacitance.  The coupler would open if it weren't coupled to a car; but, if coupled (which is of course when you need it), the locomotive couldn't move away quickly enough, and the knuckle stayed closed.  So the relay is just for switching track voltage to the coupler; and the capacitor is upstream of the relay coil.  Here is the circuit:

    1N4148  1 kohm        1N4148
+ ---->|------/\/----------->|---
                   |     |      |
                   |   relay    |
                 | /    coil    |
         1 kohm  |/  2N  |      |
field------/\/---|\ 3904 -------|
                 | v            |+
                   |     1000 uF=
                   |            |
                   |            |
- -------------------------------

        relay
pickups---X----coupler---frame

I could have used another relay to detect the startup (and postwar Lionel could have too), but I used a transistor instead.  The startup is sensed from the motor field-coil voltage.  My locomotives all have rectifiers, but the circuit is easy to adapt to AC.  Any sensitivity changes would be made by changing the 1-kilohm charging resistance.

One other change from the original design was to arrange the discharge circuit so that no charging current gets to the relay coil while the transistor is on.  Originally, the charging circuit just connected directly to the capacitor; but the charging current was enough to occasionally hold the relay operated indefinitely.

By the way, the circuit can be located in the tender or in the locomotive.  In the former case, you need a tether wire to sense the field voltage; in the latter case, you need a tether wire to get the uncoupling voltage to the coupler.

[webenda]

[cwburfle]

Tootle: Did you look at my suggestions? Were they of any help?

So far, nobody else seems to have any ideas.

[webenda]

Something like this?

[lionelsoni]

"The circuit charges a capacitor when track voltage is raised for a few seconds while the locomotive is in neutral."  To uncouple, I have to give it substantially more voltage than it takes just to cycle the e-unit and for substantially longer than I would usually linger in neutral.

I very rarely accidentally uncouple; and I would bet that if you had operated my trains without knowing about this feature, you would never notice it.  In any case, the amount of charging (voltage x time) needed to operate the relay can easily be set to any desired insensitivity.

Imagine shoving some cars into a siding or a yard, then cycling into neutral and staying there with full track voltage for, say, five seconds, then cycling into forward and pulling away from the cars.  That's how I typically use it.  If I should be running forward and want to park in neutral, no harm is done, since I have to go through reverse before getting back to forward when starting up again, and the couplers are not going to separate in reverse, even if the train doesn't move backward a little.

[webenda]

lionelsoni

Then, the next time the motor starts up, it dumps the capacitor's charge into the coil of a small relay, which operates the coupler for a moment from the track voltage..

Bob,

I am confused. Each time you move from neutral to forward or reverse, the engine uncouples from the train?

Let me imagine this. I start the engine in forward motion and it uncouples from the train. So I cycle through neutral to reverse and couple up again. Then I cycle through neutral and as I start to move forward, it uncouples again.

I don't understand how your circuit could be useful.

[cwburfle]

One more thought:

Is the baseplate mounted to the correct axles?
It should be on the two axles closest to the coupler or drawbar. The collector should be hanging inbetween the two axles closest to the center of the tender.

[cwburfle]

I haven't seen your particular problem.
Just a WAG:

Check the condition of the conical springs that apply downward pressure on the roller bracket. It is on top of the roller bracket, between the bracket and the head of the rivet.
I wonder whether a missing or weak spring lets the bracket move from side to side.

Also, is the baseplate tight on the axles?

[lionelsoni]

What I have done with all my locomotives, postwar and modern, that have electromagnetic couplers is to install a circuit that I devised to allow them to uncouple anywhere.  So I don't have a single blade-type uncoupling section on my layout.

The circuit charges a capacitor when track voltage is raised for a few seconds while the locomotive is in neutral.  Then, the next time the motor starts up, it dumps the capacitor's charge into the coil of a small relay, which operates the coupler for a moment from the track voltage.  It does require a one-wire tether between a steam locomotive and its tender.

[Tootle]

I’m trying to solve a problem with nuisance activation of the coil coupler on my 2671W tender.  The coupler truck is a short articulated light coupler truck with both a pickup shoe for the coupler and a pickup roller for whistle and lighting.  The problem seems to be mainly with OTC lockons whereby the pickup roller shorts the center rail to the lockon blade while the pickup shoe is still in contact with the blade, thus energizing the coil and opening the coupler.  There seems to be just enough play/slop in the roller/bracket/spring assembly to allow the roller sufficient lateral movement that it shorts the center rail to the OTC blade.  It doesn’t happen every time the truck passes over an OTC, but with sufficient frequency as to create a nuisance.  I’ve tried this with two similar trucks over two different OTCs and gotten similar results.  As an aside, the anomaly also manages to momentarily energize the accessory connected to the OTC, e.g., the horse corral, such that one wonders why it is that the horses seem to have moved around the corral by themselves.

I suppose I could try shortening the OTC blades or fitting smaller rollers, but I’d like to get some other ideas as well.  Has anyone had similar experience?  Any suggestions on a fix, or shall I simply relocate the OTCs and accessories to sidings and keep them off the main line?  Thanks.